Dumont et al. recently suggested that the springtime darkening of the Greenland Ice Sheet since 2009 is a consequence of an increased load of light-absorbing impurities in snow. They proposed that the impurities consist of soot or dust derived from new snow-free areas. Dumont et al. mention microorganisms as potential light-absorbing impurities, but do not incorporate biological activity into their numerical snow model. Here scientists argue that microorganisms, such as the pigmented algae that reside in snow and ice, can cause a substantial reduction in albedo and that this effect needs to be included in numerical albedo models of the Greenland Ice Sheet. [Source: Nature Geoscience]